Hi Yiangos,
How have you been getting on since? I have a 5kW R290 FTC7 and am getting the exact same issue as you because I am right on the minimum limit for the heat pump.
I have noticed that just before the cycling starts, the flow temperature starts to creep up (I assume the FTC7 is doing that to stay within the design envelope, either that or my emitters aren’t rejecting enough heat) but then when the flow temperature gets to 2°C higher than the set point it must trigger some other logic in the FTC7 to shut off the compressor, then the cycling begins.
The only way to output more heat from an emitter is either increasing the delta T (at the same flow rate) or increasing the flow rate (at the same delta T). Increasing the flow temperature usually also increases the delta T and reducing flow rate usually also increases delta T, but increasing temperature is the opposite of what we want and reducing flow has its limits too.
I would be interested to hear how you are getting on, ultimately I think the problem is the heat pump is too big for the heat demand.
| Cp (kJ/Kg.K) | DT (K) | Q (L/s) | Q (L/min) | Power (kW) |
|---|---|---|---|---|
| 4.18 | 1 | 0.150 | 9 | 0.63 |
| 4.18 | 2 | 0.150 | 9 | 1.25 |
| 4.18 | 3 | 0.150 | 9 | 1.88 |
| 4.18 | 4 | 0.150 | 9 | 2.51 |
| 4.18 | 5 | 0.150 | 9 | 3.14 |
| 4.18 | 6 | 0.150 | 9 | 3.76 |
| 4.18 | 7 | 0.150 | 9 | 4.39 |
| 4.18 | 8 | 0.150 | 9 | 5.02 |
| 4.18 | 9 | 0.150 | 9 | 5.64 |
| 4.18 | 10 | 0.150 | 9 | 6.27 |
| Cp (kJ/Kg.K) | DT (K) | Q (L/s) | Q (L/min) | Power (kW) |
|---|---|---|---|---|
| 4.18 | 1 | 0.300 | 18 | 1.25 |
| 4.18 | 2 | 0.300 | 18 | 2.51 |
| 4.18 | 3 | 0.300 | 18 | 3.76 |
| 4.18 | 4 | 0.300 | 18 | 5.02 |
| 4.18 | 5 | 0.300 | 18 | 6.27 |
| 4.18 | 6 | 0.300 | 18 | 7.52 |
| 4.18 | 7 | 0.300 | 18 | 8.78 |
| 4.18 | 8 | 0.300 | 18 | 10.03 |
| 4.18 | 9 | 0.300 | 18 | 11.29 |
| 4.18 | 10 | 0.300 | 18 | 12.54 |